A transmissive or transflective liquid crystal display device includes a liquid crystal display panel and a planar light source device (a so-called backlight) disposed behind the liquid crystal display panel. In this type of liquid crystal display device, planar light projected from the planar light source device is used to display an image on a display screen of the liquid crystal display panel.
An edge (side) light type planar light source device is known as the planar light source device, which has a configuration such that a linear light source, which defines a member consisting of a substrate and a plurality of LED chips that are aligned on the substrate, or a cold cathode fluorescent tube, is disposed along an end face of a light guide plate that defines a clear plate made from an acrylate resin. In this type of planar light source device, the light emitted from the linear light source is guided to the inside of the light guide plate from the end face of the light guide plate, and thereby the guided light is made into planar light and emitted from a front face of the light guide plate. The light guide plate includes scattering members in a dot pattern that are disposed over a back face of the light guide plate and arranged to scatter the light that enters from the end face of the light guide plate. In addition, a reflection sheet arranged to reflect the light is provided on the back face of the light guide plate. Thus, the light emitted from the linear light source as described above is scattered or reflected by the scattering members or the reflection sheet, and thereby the light is made into planar light and emitted from the front face of the light guide plate.
PTL 1 discloses this type of planar light source device, which includes a light guide plate on a peripheral portion of which, a notch or through hole for disposing or fixing the light guide plate to a chassis is provided. The notch or through hole is disposed inside of a peripheral end face of the light guide plate having a rectangular shape. The light guide plate is disposed or fixed to the chassis with the use of a projecting locking member such as a pin that erects from the chassis and is inserted in the notch or through hole.
Having this configuration, the light guide plate does not need a convex portion to be disposed outside of the peripheral portion as shown in PTL 2 for the purpose of disposition of the light guide plate. Thus, every end face of the light guide plate has an almost straight (almost flat) shape. The planar light source device including the light guide plate described above is capable of having the linear light source disposed along any end face of the light guide plate. In addition, the planar light source device including the light guide plate described above is preferably used together with a liquid crystal display panel having a narrow nondisplay region that surrounds a display region (i.e., a liquid crystal display panel having a narrow frame region).